Controlling fuel vapor in vehicle fuel tanks has long been an objective for automobile manufacturers and suppliers of fuel systems components. Fuel vapor can be created in the fuel tank by temperature differences between the fuel tank and liquid fuel from a fuel pump, as well as by sloshing and agitation of the fuel tank during normal vehicle operation. The vapor collects in various high points within the fuel tank, and is normally released from the fuel tank through one or more vent valves located within the wall of the fuel tank. This prevents pressurization of the tank or the creation of a vacuum therein as a result of fluctuations in fuel volume due especially to changes in temperature or in atmospheric pressure or to the drop in fuel level as the fuel is drawn off.
Once the fuel vapor has been discharged from the fuel tank, the vapor must be adequately stored and/or consumed to assure compliance with air pollution regulations. In some vehicle fuel systems, discharged fuel vapor is exhausted to a charcoal-filled vapor recovery canister designed to capture and store fuel vapor. These so-called “on-board” fuel vapor recovery systems are disclosed, e.g., in U.S. Pat. Nos. 4,770,677; 4,816,045; and 4,836,835. Other systems route the fuel vapor back to the engine, where it is combusted.
Due to the size restraints of the vehicle, the fuel tank may have a complex shape. It often includes pockets in its upper wall, or areas liable to collect fuel vapor when the fuel reaches a high level in the tank and/or when the vehicle is on an incline. Each of these pockets therefore requires a means of venting the collected vapor to the outside of the tank. Multiple ventilation point may be connected directly to the outside of the tank, but due to permeation of fuel vapor through multiple vapor vent lines, increased vapor emissions are eminent.
With the increasing requirements to reduce emissions, it becomes advantageous to route vapor vent lines inside the fuel tank, to a single exit point from the various vapor pockets created within the tank. Doing so reduces permeation emissions by containing multiple vapor lines inside the fuel tank. Furthermore under these increasing regulations to reduce emissions, where multiple vent valves used to be mounted in separate apertures through the fuel tank, it now becomes advantageous to mount them within the fuel pump mounting flange, thereby eliminating the need for additional holes through the tank and potential vapor emission sources.
The need arose for a fuel pump module with an integrated manifold, combining the fuel vapor from multiple sources within a fuel tank, and discharging them through a single outlet port, located on the pump modular flange.